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Moving away from the midlength's

John A.

John A.

Unconstitutional laws are not laws.
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While I'll be the first to say that I was never a big fan of the 16 inch midlength gas systems, the 18 midlengths are more appropriate where dwell time is concerned and the first midlengths were 18 inch barrels in the SPR project were designed as such.

The 16 inch midlength barrel I have initially had some issues with the gas port being too small which caused short stroking, feed/ejection problems and just generally gave me fits until I enlarged the gas port to the industry average gas port diameter (.080")

So, when a guy on another forum was looking for some build parts, he decided that he'd want the barrel assembly and some other parts I've had collecting dust , so I'm finally going to do the pencil barreled 20" retro build that I always wanted to do.

It's not going to be 100% period correct (nor am I interested in making it that way), but will be strongly reminiscent of it's early roots.

I just hope the pencil barrel is comfortable and not very front heavy. Website says (minus handguards) is 2.37 pounds, and the 16 inch middy barrel that's on it is heavier than that, so I'm hoping that it's a comfortable shooter when I'm done.

Everyone should have at least 1 AR rifle in their collection. Seems like the rage the last few decades are almost entirely carbines, but rifles still have a few things that make them stand tall.

A quick sneak peek so far.

df55ea39-2721-44e9-9555-f118df4e29c7_zpsuxeci2bl.jpg
 
Got the midlength barrel assembly off.

It weighed more than I thought.

40 ounces even (2-1/2 pounds), minus handguards.

I think I'll weigh the 20 inch assembly just to get an idea of where I'm coming in weight wise.

midlength barrel assembly weight 002.JPG
 
It won't be anything groundbreaking, but there will be some "enhancements" that weren't thought of or available back in the 70's. I do so wish I could find a lightweight/pencil barrel in 1:7 and nitride treated, but they don't exist in that configuration. (I'm beginning to be a huge fan of nitride gun parts).

I believe most of the little upgrades will probably be overlooked entirely as they'll be internal.
 
About like this.

Kinda.

Sorta.

tod.jpg

for extra credit, does anyone else remember this show?
 
Gonna ear mark that one for later. You going flat top upper, with detach carry handle? Or one piece forging?
 
You goy my attention.

Ive been wanting to build a 20" upper for a while. It just seems that 16" barrels keep falling into my hands and budget.
 
@dieselmudder the correct and proper upper for this receiver is an A1, which I have no problem with and to be truthful about it, my first AR was an sixteen inch A1 CAR made before flat tops even existed, but I already have a flat top upper and a detachable carryhandle, so that's what I'm going to use. And besides, the upper and lower fit each other like they're made for each other and like a matched pair.

OAPlinker001.jpg


MikeD, I have a few 16 inch carbines on hand already and I know what you mean. But have wanted to build a 70's style rifle for a while. To be honest, I've always wanted one of these variants. So, there is no better time than the present. Seems like all the original parts needed to make one of these, the part supply is drying up pretty fast. Especially the triangle handguards.
 
My rifle started as a 20" Gov profile CHF rifle. BUt has since made the change to an 18" match stainless heavy, fluted, rifle length gas barreled rifle. The 18 barrel is way more accurate, but that has more to do with quality of barrel than the length. I went from 20" to 18" due to the length of the compensator I put on her. The 3" comp made the 20" rifle feel like a broom handle.
 
Once upon a time, I had a 24 inch upper that I used for precision work. Adding a 10 inch suppressor to it looked absolutely ridonkulous.

longrangerhighdefroad.jpg
 
Parts are starting to stream in slowly now.

With yesterday being Veterans Day, delayed most stuff by another day, but I'm not pressed for time, so I'm not worried about it.

The barrel got here yesterday (That was fast, thanks Del-Ton.).

For comparison, the 20 inch lightweight weighs a whopping total of 1 ounce more than the 16 inch midlength barrel that was on it, so I'm thankful that it's not going to be terribly front heavy.

And besides that, the longer barrel is going to give me more velocity, and an extended sight radius with the irons may lend itself to being a little more accurate.

middy
midlength barrel assembly weight 002.JPG

Rifle
retro build 001.JPG
Upon test fitting the upper and barrel, I found out that the M4 upper receiver notches aligned flawlessly with the barrel extension. That was something of concern because most older rifle barrel extensions do NOT have m4 feedramp notches and have been known to cause issues feeding issues with mismatched combinations.

But these both have M4 feedramps and they line up like they're made for each other so that's good.

I'm going to try to rescue some of the other parts from the P.O. this evening. With any luck I'll be able to lap the upper receiver this evening so I can at least get the barrel mounted afterwards.
 
It was a no-go at the post office this evening.

Apparently, if a company ships an item with surepost now, the post office isn't allowed to let the addressee pick it up at the window anymore, unless you wait until the following day when USPS is supposed to deliver it, so that puts this project 2 days behind now.

I swear, the postal service around here is sucking more all the time.

It's not that I can't wait until tomorrow to finish it because I can, but to be perfectly honest, the package does belong to me and I have paid for it. Yet the postmaster says she's not allowed to let me have it. Good grief. Are you kidding me?
 
Looking forward to the build. I lapped my Grendel upper last night. Attempted to take pictures of the process. But lighting in my barn was poor. Ended up taking about 10, ten second runs with 220 grit to get an even shiny surface all the way around. I used a standard automotive chassis grease to live the lapping tool
 
Did you notice any high or low spots when you first got started?

I'm glad you got your upper lapped and squared up. And I'm surprised it went so quick.

I want to do it mainly to keep the bolt lugs and the barrel extension as straight as possible with as little stress on them as I can. Though ensuring the barrel is straight isn't going to hurt anything there either.

The lapping tool and compound is one of the things in the box that I couldn't get today.

In other news, I got a shipping notification that the triangle handguards shipped today. Coming from PA, I should get them by Saturday with any luck.

But with that way that's been going lately, who knows.
 
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